Plant bugs increasing pest in Louisiana cotton

The competition for worst pest in Louisiana cotton once had more contenders than it does today. The arrival of biotech varieties a few years ago rapidly knocked several — among them, budworms and bollworms — out of the medaling. One of their replacements, said Ralph Bagwell, has been the reinvigorated plant bug.

“We deal with four primary plant bugs in U.S. cotton: the western tarnished, the fleahopper (a problem in Texas), the clouded plant bug (a problem in north Arkansas and Tennessee), and the tarnished plant bug,” said the LSU AgCenter entomologist, who spoke at the Louisiana Cotton Forum in Monroe, La. “The tarnished plant is a ubiquitous pest — it's pretty much anywhere in the country. For instance, it's a pest of strawberries in New Jersey.”

Over the last decade, said Bagwell, there have been “very significant changes” in tarnished plant bugs.

“I consider it almost a completely different insect than it was before because of the way we have to deal with it now. It's changed incredibly since 1995. In the past, we were primarily dealing with weevils, bollworms and budworms. Sure, we treated for tarnished plant bugs, but we spent the bulk of our treatment money on the others.”

With the elimination of weevils through eradication efforts and the arrival of Bt cotton, the significance of plant bugs has increased. There's also been a big increase in cotton damaged by the pest.

“That was pretty much the only problem we had with them. They weren't much of a problem after first bloom because they didn't appear to feed much on bolls. In retrospect, the insecticides we were putting out for weevils and worms were giving us coincidental control of plant bugs. Once those treatments were eliminated, plant bugs moved in and fed in different plant areas and at different times of the season.”

Now, plant bugs are a “true villain. Today, I see more injury from this insect after first bloom than before.”

More hosts

There also has been a move to more hosts for the pest. In 1998, Louisiana grew 1.1 million acres of cotton.

“We were primarily a cotton monoculture — everywhere you looked was a cotton field. Currently, we're planting all kinds of other crops. Many former cotton fields have been moved into federal programs like CRP and WRP. Those areas provide additional hosts for plant bugs.

“This pest can feed on just about anything — if it's a broadleaf, it's a meal.”

Control

Bagwell has seen a “fairly significant” change in the ability to control plant bugs. “A few years ago, we put out a quarter-pound (per acre) of Orthene or Bidrin and controlled plant bugs very well. I can't remember the last time we put out even a third of a pound of Orthene and expected even decent control. There has been a huge shift in how we're able to control plant bugs.”

Properly managing today's plant bugs includes developing new guidelines for sampling procedures, thresholds, and new control practices. Current sampling procedures are based primarily on scouting for plant bugs as a pre-bloom pest, not as a post-first bloom problem.

“We are involved in an integrated effort with several states to identify the most effective means of sampling post-first bloom. Also, we want to know the most efficient means of sampling.

“Many states recognize the problem. There is also support from some state committees. We desperately need answers.”

As far as control difficulties, “we're not going to see many new insecticides. There is no question about that.

“Why are we having this problem? Simply because when you go before the EPA or another regulatory agency and say, ‘We need some relief,’ they say, ‘well, look at this long list of products you have already.’

“They won't look from the farmers' perspective, wanting something cheap and effective. Acephate is left, and Bidrin, hopefully, will be for a few more years. Beyond that, there isn't much. We shouldn't depend on just one class of products. That's especially true with plant bugs that can develop resistance.”

Once new sampling procedures are in place, treatment thresholds will be considered. “Right now, consultants' threshold recommendations across Louisiana bounce here, there and yonder.”

Bagwell points to a photograph of someone sitting beneath banana trees. In the background is a cotton field.

“I like this picture. How many times have you seen bananas growing next to cotton? Not often, I'd guess.”

The point of the photo, he said, is to always pay attention to what is growing adjacent to cotton. Insect densities are often greatest on borders as pests move from alternate hosts into fields.

“The more you can isolate a cotton field, the less you'll have to spray for insects. The more you piecemeal your cotton and jigsaw it with other crops or host plants, the greater the likelihood of a pest infestation.”

Use records for tracking. “When your consultant writes something down, that's a record for tracking. When you go to an airport and tell them to spray, that can be tracked. It helps us recognize what needs to be done.”

But those records can also be used by others. Be careful. “A consultant called wanting to know about putting Ammo on soybeans. I said, ‘Whoa, hang on. Ammo isn't labeled for anything but cotton.’ He said, ‘Oh, I'm glad I called because I was going to take that order to the plane.’”

Another consultant asked Bagwell about putting out 1.5 pounds of Orthene. “Whoa, again! Orthene is only labeled up to a pound. Pay attention to these things. We don't want to get into a situation similar to when Fury was sprayed on Arkansas wheat.”

Since Bt cotton was introduced, there's been a reduction in compliance with resistance management.

“I know we don't have a problem in Louisiana, but outside in some spots they do. A lot of growers aren't planting refuges, and Monsanto has turned in some reports to the EPA.”

The Louisiana Department of Agriculture understands the long-term value of Bt crops, he said. As a result, the department “will be checking quite a few growers to make sure they have set up refuges properly. Corn planting is coming up, and they're talking about monitoring Bt corn. You can't plant more than 50 percent Bt corn.”

From a resistance management standpoint, this is very important.

“I was on a panel on Bt resistance and the like several years ago. Public comments were being heard at the same time. Everyone who wanted to talk got five minutes.”

One of the first speakers, Bagwell said, was a prominent cotton producer from Alabama. He spoke on how important Bt cotton was for his allotted five minutes.

“The very next person was a small girl from upstate New York representing Greenpeace. She'd never seen a cotton plant before. But she started telling everyone how bad this technology was and how it would create resistance to many insects. I thought, ‘You know the most important thing to learn here is this little girl has just as much impact as the farmer.’

“If resistance to this technology ever develops, the first thing that will happen is the environmental groups will yank it out from under us. They'll put on a full-court press to get rid of all transgenics. They'll use resistance as the means to do it.”

If resistance occurs, “We want to be in a position to say, ‘No. We did what we were told and broke no rules. We planted refuges just like we were told.’”